Rainfall

The total October rainfall of 27.0 mm at Sydney Observatory Hill was
well below the historic October average1 of 77.0 mm. There were only 5rain days
during the month, also below the October average of 11 rain days. Monthly
rainfall totals were below
average over the entire metropolitan area with the lowest in the western suburbs, particularly
the south-west. Totals ranged from 49 mm at Merrylands West to only 11.2 mm at Camden
Airport. Much of the rainfall occurred during thunderstorms caused
by the passage of several low-pressure troughs. Thunderstorms were most active in
the Parramatta, inner west and North Shore suburbs where some
localised heavy falls and flash flooding occurred. At Merrylands West 36mm was recorded in about 15
minutes on the 26th.

The Warragamba Dam catchment
received only light rainfall during October, with storage levels falling
slowly.
Monthly totals over the catchment were generally in the 15-30mm range. Recent rainfall in Sydney's drinking
water catchments can be found on the Sydney Catchment Authority web site
http://www.sca.nsw.gov.au/dams/rainfall.html.

Temperature

The average maximum (daytime) temperature at Observatory Hill was 25.0°C, which
is well above the historic average1 temperature of 22.2°C.
This is the 3rd highest average maximum temperature on record
for October and the highest since 1988 (when Sydney
recorded its hottest October on record). It was even warmer in the western suburbs
with an average maximum temperature at Richmond of 27.4°C
(3.0°C above the historic average).
Sydney experienced several days of hot weather caused
mainly by brief spells of hot NW winds. There
were 5 days when the temperature exceeded 30°C at Observatory
Hill, the highest number since 1988. Normally Sydney would
expect 2 days over 30°C in October.

Over the last 10 years, there has been nine Octobers with above average maximum temperatures
and only one below average.

Night-time temperatures were very mild along the coast but cooler
over inland suburbs. The average minimum temperature of
15.7°C at
Observatory Hill was 1.6°C above the historic
October average1 and the 3rd highest on record (records
since 1859). However, minimum temperatures were several
degrees cooler in far western suburbs and up to 6°C cooler
at Camden. The
average at Camden (9.5°C) was slightly below the historic
October average.

Coastal Sydney experienced many mild to warm nights - at Observatory
Hill there were 17 nights when the temperature did
not fall below 16°C, a record for October. The previous highest was 15 nights
above 16°C in October 2005 (records from 1859). Normally Sydney would
expect 7 nights above 16°C in October. On the 29th, the warmest night of the month, the minimum
temperature at Observatory Hill was 21.3°C or more than 7°C above average. The
highest minimum temperature in the metropolitan area during October was 21.6°C at Parramatta
and Sydney Airport on the 29th; the warm conditions on this night were
caused by heavy cloud cover
and moderate northerly winds.

The highest temperature at Sydney (Observatory Hill)
during October was 34.8°C on the 3rd while the lowest temperature was 10.5°C on the
13th. Corresponding extremes in the Sydney
metropolitan area ranged from 36.2°C at Sydney Airport on the 13th to 3.4°C at Camden on the 5th.

Wind

There were 11 windy days as measured at Sydney Airport, compared to an average of 6. The highest wind gust recorded was 89 km/h at Sydney Airport on the 3rd and 6th.
Except for brief spells of warm westerly winds, the prevailing
direction was between E and S.

Other phenomena

There were 5 days with thunderstorms in Sydney during October compared to
the historic average of only 2 storms. There were 2 severe
storms producing hail and flash flooding. On the 12th, 4cm size
hail was reported at Camden Airport and 2cm hail at Heathcote.
On the 26th, heavy rain, local flash flooding and power outages
occurred in the Ryde area.

On several days during the month hot,
dry westerly winds caused very low humidity levels in Sydney. On
the 3rd the humidity fell to a very dry 8%, the lowest reading in October
since 1991 and one of the lowest ever recorded in October. Similar
low humidity occurred on 1st, 16th and 29th. Strong
winds and high temperatures on these days created a very high bushfire
danger with fires burning over 300 hectares of bushland in Ku-ring-gai
Chase National Park and at Cowan in Sydney's north on the 2nd and
3rd. Sunshine was plentiful during October with an average of 8.9
hours per day, the highest since 2001.

Notes

This statement has been prepared based on information available at
12 pm on Thursday, 1 November 2007.
Some checks have been made on the data, but it is possible that results will change
as new information becomes available.

1Averages: historic average temperatures for
Observatory Hill and Richmond are based on the period 1961 to 1990 which is a convention of the World Meteorological Organisation.
Average temperatures for Parramatta are based on all available
data, 1968 - 2006 and Camden 1972 - 2006. Rainfall averages
and extremes for Observatory Hill are based on all years of record
1859 - 2006.

Normals are long-term means based on observations from
all available years of record, which vary widely from site to site.
They are not shown for sites with less than 10 years of record, as they cannot then be calculated reliably.
The median
is sometimes more representative than the
mean
of "normal" rain.

The Rank indicates how rainfall this time compares with the climate record for the site,
based on the
decile ranking
(very low rainfall is in decile 1, low in decile 2 or 3,
normal in decile 4 to 7, high in decile 8 or 9
and very high is in decile 10).
The Fraction of normal shows how much rain has fallen this time as a
percentage of the long-term mean.